Fig. 8

Distribution of the estimated stress field in the Tohoku District inland area. Each result is plotted, \(1^\circ \times 1^\circ\), at the center of each sub-area. A, B The events that occurred from January 1, 1997 to March 10, 2011 (before the Tohoku-Oki earthquake) and from March 11, 2011 to December 31, 2019 (after the Tohoku-Oki earthquake), respectively. The results are shown using lower hemisphere projections. Red, green, and blue circles denote the optimal solution for \({\sigma }_{1}\), \({\sigma }_{2}\), and \({\sigma }_{3}\), respectively. Small pastel red, green, and blue without outlines denote the 95% confidence ranges for \({\sigma }_{1}\), \({\sigma }_{2}\), and \({\sigma }_{3}\), respectively. The black line and gray fan denote the best and the 95% confidence ranges for the \({S}_{Hmax}\) orientation, respectively